Vacuum chambers and other vacuum systems, together with residual gas analyzers (RGAs), can be used in various processes or devices. Examples include coating machines for semiconductors or non-semiconductors, including physical vapor deposition (PVD) machines, chemical vapor deposition (CVD) machines, and atomic layer deposition (ALD) machines; leak detection; atmospheric measurement systems, e.g., used at oil-drilling sites; food or pharmaceutical analysis systems; chemical weapons detectors; particle accelerators; and research and development equipment.
For example, the process of making semiconductors, e.g., integrated-circuit transistors, involves numerous processes carried out under very low pressures. These pressures are maintained in what are commonly referred to as “vacuum chambers.” In general, a vacuum chamber is an enclosure connected to a pumping system, e.g., one including a cryo pump or turbopump. The pumping system maintains low or extremely low pressures, e.g., 10−8 Torr for a base pressure or 5 mTorr during processing. The pumping system can maintain specified concentrations of selected gasses in the chamber. A “vacuum tool” is a device that includes one or more vacuum chamber(s) and facilities to transfer workpieces in and out of the vacuum chamber(s). An example of a vacuum tool, specifically a cluster tool, is the ENDURA PVD machine made by APPLIED MATERIALS. For example, PVD processes for depositing copper (Cu) and tantalum nitride (Ta(N)) require vacuum, e.g., ˜5 mTorr. Throughout this disclosure, “vacuum” refers to pressures much lower than atmospheric (1 atm=760 Torr), e.g., <20 Torr.
Various silicon-wafer semiconductor processing plants (“fabs”) use partial pressure analyzers (PPAs), e.g., residual gas analyzers (RGAs), to test vacuum chambers. RGAs perform mass spectrometry on atoms (e.g., argon gas), molecules, or other charged particles in chambers to determine the composition of those molecules or their partial pressures. RGAs can include quadrupole mass spectrometers or other filters to select ions with particular characteristics, and detectors to detect or count the selected ions. RGAs and are widely used for in-situ process monitoring in semiconductor manufacturing, especially in PVD processes. Among the uses of the PPA for CVD or etching processes are: following the process chemistry by monitoring the timing and concentration of input gases; monitoring reaction products; eliminating waste; and assessing the of the process chamber, e.g., by checking for leaks, residual contaminants, contaminants during processing and proper functioning of the tool. PPAs for CVD/etch applications can use a closed ion source (CIS) or an open ion source (OIS). There is a continuing need for improved RGAs or RGA detectors.